Emerson Rosemount 3101, Reference Manual

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10
Reference Manual
00809-0100-4840, Rev CB
Section 3: Installation
February 2015
Installation
3.3 Mechanical installation
3.3.1 Mounting considerations

Mount the transmitter above the liquid using the 2-in. thread provided, but no closer
than 12 in. (0,3 m) to the surface. The transmitter does not detect any liquid surface
closer than 12 in. (0,3 m) to the transmitter face. (See
“Mounting the transmitter above
the liquid surface” on page 12 ).
Optional flanges and bracket kits are available to help mounting
(see “Spare parts and accessories for the 3101/3102/3105” on page 90 ).

The transmitter should be mounted vertically to ensure a good echo from the liquid
surface. The transmitter beam half angle is 6 degrees (see
Figure 3-2 on page 11 ).

Obstructions in the tank, or well, may generate echoes which can be confused with the
real liquid surface echo. Obstructions within the beam angle generate strong false
echoes. Wherever possible, the transmitter should be positioned to avoid false echoes.

To avoid detecting unwanted objects in the tank or well, it is advisable to maintain a
distance sideways of at least 1.3 in. from the center line of the transmitter for every foot
(11 cm per meter) range to the obstruction (see
Figure 3-2 on page 11 ).

No false echoes are generated if the transmitter is located near the side of the tank or
well, and the wall is smooth and free of protrusions. However, there will still be a
reduction in the echo size. It is recommended that the transmitter be mounted no
closer than 12 in. (0,3 m) to the wall to avoid a large reduction in the echo size.

If the transmitter is mounted in an enclosed tank with a domed top, avoid mounting
the transmitter in the center of the tank roof because this could act as a parabolic
reflector and create unwanted echoes.

Avoid applications where heavy condensation could form on the transmitter face.

If the transmitter is mounted in a stand-off or nozzle, the transmitter face should
protrude at least 0.2 in. (5 mm) into the tank. If this is not possible, see
“Mounting the
transmitter above the liquid surface” on page 12 ).

If the transmitter is used in environments where direct sunlight can cause high
temperatures on exposed surfaces, a sun-shade is recommended.

Check that the maximum liquid level will not enter the 12-in. (0,3 m) blanking zone of
the transmitter.
3.3.2 Consider liquid surface conditions

Foaming liquids can reduce the size of the returned echo because foam is a poor
ultrasonic reflector.
Mount an ultrasonic transmitter over an area of clear liquid, such as near the inlet to a
tank or well. In extreme conditions, or where this is not possible, the transmitter may
be mounted in a vented stilling tube provided that the inside measurement of the
stilling tube is at least 4 in. (100 mm) and is smooth and free from joints or protrusions.
It is important that the bottom of the stilling tube stays covered to prevent the ingress
of foam.